1. Field of Invention
This invention relates to a gear changing device, for use in a communication apparatus, such as a facsimile machine, that changes gears according to the switching of modes, for instance, between an image reading mode, recording mode, and copying mode. This invention also relates to a communication apparatus including the gear changing device.
2. Description of Related Art
In an operation mode of a facsimile machine, such as an image reading a mode, a recording mode, and a copying mode, only relevant gears for the operation modes need to be rotated. To achieve this, a gear changing device is devised that changes gears according to the switching of the operation modes. Such gear changing devices are disclosed in U.S. Pat. Nos. 5,764,372 and 6,178,863 B1. The gear changing device disclosed in U.S. Pat. No. 5,764,372 includes a control motor, two sun gears, two planetary gears, and a switching cam. The gear changing device disclosed in U.S. Pat. No. 6,178,863 B1 includes a control motor, a sun gear, two planetary gears, and a solenoid. As the sun gear rotates in the forward or reverse direction, the planetary gears are pivotally moved clockwise or counterclockwise, selectively engaging with transmission gears. Accordingly, the drive force of the sun gear is transmitted to a plurality of transmission paths. Because the pivotal movement of the planetary gears may or may not be prevented depending on the phases of the switching cam or by turning the solenoid on or off, the planetary gears are selectively engaged with the transmission gears in each of the operational modes. Thus, the drive force of the sun gear is selectively transmitted to the transmission paths.
Such known gear changing devices require a large number of parts other than the sun gear and the planetary gear, leading to complicated structures, as well as making the gear changing device larger in size. Consequently, a communication apparatus including the gear changing device naturally becomes larger in size, so that the reduction of the physical size of the communication apparatus is difficult to achieve.